FIG. 4 shows a conventional SEPP (Single Ended Push-Pull) type vertical deflection circuit comprising a single power source.
An input terminal 1 for receiving a saw-tooth wave signal is connected to the non-inverting input terminal of a power amplifier 2. The output terminal of the power amplifier 2 is connected to an output terminal 3 and at the same time is grounded through resistors R1 and R2. The node of the resistors R1 and R2 is connected to the inverting input terminal of the power amplifier 2. A series circuit of a vertical deflection coil L, capacitors C1 and C2, and a resistor R3 is connected between the output terminal 3 and the node of the resistors R1 and R2. The node of the capacitors C1 and C2 is grounded through a resistor R4.
The resistors R1 and R2 are negative feedback resistors for determining the DC operating point of the output signal of the power amplifier 2. The capacitors C1 and C2 are DC-blocking capacitors. Especially, in an SEPP type vertical deflection circuit comprising a single power source, the capacitor C1 operates as a power source during a negative half cycle. Therefore, an electrolytic capacitor having a large capacitance of about 1,000 .mu.F is used as the capacitor C1.
In the above arrangement, assuming that the DC voltage is Vref with no signal being input to the input terminal 1, the potential Vo at the output terminal 3 is: EQU Vo=Vref(R1+R2)/R2
On the other hand, during AC operation, i.e., when a saw-tooth wave signal is input to the input terminal 1, the capacitors C1 and C2 are conductive. Thus, an AC power amplification factor Gv is approximately: EQU (R3+R2)/R2 EQU (X.sub.c1, X.sub.c2 &lt;&lt;R1.about.R3, R3&lt;&lt;R1)
where:
X.sub.c1 =reactance of capacitor C1 PA1 X.sub.c2 =reactance of capacitor C2
During an AC operation, a feedback occurs from the node A of the capacitors C1 and C2, and accordingly, a negative feedback occurs such that a signal generated in the resistor R4 becomes Gv times an input signal. As a result, assuming that an input signal is Vin, a current EQU (Vin.multidot.Gv)/R4
having a good linearity flows across the vertical deflection coil L.
However, since the conventional vertical deflection circuit is an SEPP circuit having a single power source, the large-capacitance capacitor C1 is required for DC blocking. Furthermore, since an AC saw-tooth wave signal is supplied to the vertical deflection coil L, the resistors R1 to R3, the capacitor C2, and the like are also required to determine the AC and DC operating points.
Normally, the power amplifier 2 is packaged in an integrated circuit to increase the reliability and to lower the price. However, the capacitors C1 and C2, the resistors R1 to R4, and the like are components that are externally connected to the integrated circuit. When the number of components externally connected to an integrated circuit is large, the reliability is degraded and the cost increases.